Flexible distributed/centralaized architecture for voice/unified messaging system

ABSTRACT

There is provided a messaging system comprising at least one distributed front-end messaging system and a centralized data store associated with said at least one distributed front-end messaging system, in which system the centralized data store includes means for storing data associated with users of the at least one distributed front-end messaging system, the at least one distributed front-end messaging system further including a respective at least one cache means for storing at least a portion of the centralized data associated with users of said at least one distributed front-end messaging system such that at least one messaging function can be provided to users of said at least one distributed front-end messaging system in dependence on the data stored in said cache means. A centralized messaging system provides access to all stored data associated for all users associated with at least one distributed front-end messaging system.

FIELD OF THE INVENTION

[0001] The present invention relates to the field of messaging systems,and particularly to voice messaging and unified messaging systems.

BACKGROUND TO THE INVENTION

[0002] Messaging systems are well-known in the art. One of the simplestform of messaging system is a voice messaging system. Computer TelephonyIntegration (CTI) is a term which refers to the integration of computerarchitectures with telephony systems. A voice messaging system is anexample of a CTI system, and a further example is a unified messagingsystem.

[0003] Voice or unified messaging systems have conventionally beendeployed in one of three implementations.

[0004] In a first voice messaging implementation a voice messaging (orunified messaging) system is co-located with a subscriber's telephoneswitch, i.e. a subscriber's private branch exchange (PBX). Within amulti-site organization or enterprise this will tend to result in eachphysical location (which has its own telephone switch) having a separatevoice messaging (or unified messaging) system. For an enterprise withmany distributed locations, such an arrangement requires the deploymentof many (possibly small) systems resulting in considerable ITadministrative costs.

[0005]FIG. 1 shows two distributed locations each with their owntelephone switch, specifically a PBX 102 and 106 respectively, andrespective dedicated unified or voice messaging systems 104 and 108.This system provides, at least, the following three typical voicemessaging functions: call answering, automated attendant and subscriberaccess.

[0006] 1. The call answering feature is initiated when calls areforwarded by the telephone system as a result of the called party notanswering (e.g. due to a busy or no-answer condition).

[0007] 2. The automated attendant feature offers callers a menu forautomatically routing a call to the desired answering point, without theneed for operator intervention.

[0008] 3. The subscriber access feature allows subscribers, or mailboxowners, of the voice messaging system to call into the system andretrieve their messages over the phone.

[0009] In a second voice messaging implementation, the voice messagingsystem utilizes a deployment of a central messaging system servingmultiple remote locations. This form of deployment requireslong-distance telephone connections to be provided between the remoteprivate branch exchanges (PBXs), serving remote locations, and thecentralized messaging system.

[0010]FIG. 2 shows two locations each having a respective PBX 202 and204 being served by a single centralized unified or voice messagingsystem 206 associated with a single centralized PBX 208. The longdistance telephone connections generally need to be provided regardlessof their use (i.e. it is necessary to purchase enough capacity to handlebusy periods). In addition some voice messaging features are lost in thecentralized arrangement of FIG. 2. The automated attendant applicationprovides callers into an office or building with the ability to connectto a user. This capability is not provided in the centralizedarrangement of FIG. 2: the system providing the automated attendantfunction handles all users for all systems, and so does not provideservice equivalent to a human attendant at the remote site.Additionally, different offices may be located in different countrieswith different language requirements. A simple example is that a firstoffice may be in Canada and need both English and French languages,whereas another office served from the same centralized facility mayhave entirely, non-overlapping, language requirements, for examplelocated in Mexico and requiring Spanish. A common and unique numberingplan across all mailboxes across all sites is also needed.

[0011] In a third implementation the second implementation is modifiedsuch that the long-distance telephone connectivity is provided by anorganisation's (existing) data (IP) Wide Area network (WAN), possiblyusing Voice over Internet Protocol (VoIP). This deployment puts a strictrequirement on the bandwidth and more critically the quality of service(e.g. the network latency) characteristics of the corporation's WAN.This most generally is not, and will not, be met for the majority ofcorporations now or in the near future.

[0012] It is an aim of the present invention to provide an improvedmessaging system. A further aim is to provide such a system offeringincreased deployment flexibility.

SUMMARY OF THE INVENTION

[0013] In a first aspect the present invention provides a messagingsystem comprising at least one distributed front-end messaging systemand a centralized data store associated with said at least onedistributed front-end messaging system, in which system the centralizeddata store includes means for storing data associated with users of theat least one distributed front-end messaging system, the at least onedistributed front-end messaging system further including a respective atleast one cache means for storing at least a portion of the centralizeddata associated with users of said at least one distributed front-endmessaging system such that at least one messaging function can beprovided to users of said at least one distributed front-end messagingsystem in dependence on the data stored in said cache means. Themessaging system is preferably a voice messaging system or unifiedmessaging system.

[0014] There may be provided a plurality of distributed front-endmessaging systems each associated with a respective plurality of usersand each including a cache means, wherein the centralized data store isadapted to store data associated with all users of said front-endmessaging systems.

[0015] There may be further provided a centralized front-end messagingsystem associated with said centralized data store. The centralizedfront-end messaging system may be associated with a plurality of users,data associated with said users being stored in the centralized datastore.

[0016] The centralized front-end messaging system may provide at leastone messaging function for users of said at least one distributedfront-end messaging system. The centralized front-end messaging systemmay be adapted to identify the front-end messaging system of a user. Thecentralized messaging system may be adapted to identify the front-endmessaging system of a user in dependence on a called number, a callingnumber, or a unique user identifier.

[0017] The centralized messaging system may provide access to all storeddata associated with said at least one distributed front-end messagingsystem associated with the user.

[0018] The centralized data store may store configuration data andmessage data associated with all users.

[0019] The at least one voice messaging function may include callanswering. Said at least one messaging function may be a subscriberaccess function.

[0020] Each front-end messaging system may be associated with arespective Voice Mail Domain. Each front-end messaging system may beassociated with a telecommunications switch.

[0021] In a further aspect the present invention provides a method ofconfiguring a messaging system comprising: storing, at a centralizedlocation, data associated with all users of the messaging system;storing, at at least one distributed location, at least part of saiddata associated with users at the at least one distributed location, andproviding at least one messaging function to users at the at least onedistributed front-end messaging system in dependence on the data storedat the distributed location.

[0022] The step of storing the data at said at least one distributedlocation may comprise the step of caching the data at the centralizedlocation. The method may further comprise step of providing at least onemessaging function to users at the at least one distributed front-endmessaging system in dependence on data stored at the centralizedlocations. The method may further comprise the step of accessing thecentralized location directly.

[0023] In further aspects, the present invention also provides amessaging system comprising a plurality of remote servers and acentralized data store associated with said plurality of remote servers,in which system the centralized data store includes means for storingmessages and data associated with all users of the plurality of remoteservers, and the plurality of remote servers are each associated with arespective cache means for storing at least a portion of the dataassociated with users of said remote server such that at least one voicemessaging function can be provided to users of said voice serverindependent of the centralized message store. The messaging system ispreferably a unified messaging or voice messaging system.

[0024] The at least one voice messaging function may include callanswering.

[0025] The plurality of voice servers may be associated with a pluralityof Voice Mail Domains. The number of voice servers may correspond to thenumber of Voice Mail Domains. Each voice server may be associated with atelecommunications switch. The telecommunications switch may be a publicbranch exchange.

[0026] The centralized data store may further be provided with acollection of front end servers or a single server, said interface beingconnected to a dedicated telecommunications switch, such a privatebranch exchange. Such switch may provide subscriber access to thecentralized data store.

[0027] The centralized data store may provide a common message store forall voice mail domains and a common directory store for all voice maildomains.

[0028] There may be provided for subscriber access to the centralizeddata store via said interface.

[0029] In accordance with embodiments of the invention the messagingfunction is architecturally split into a number of separate componentswhich, critically, can be implemented in at least two separate computersystems. These systems can be deployed:

[0030] i. In separate physical locations connected using a data network.The message storage can be centralized within a single (or few) datastorage facilities, providing security, simplicity and management costsbenefits.

[0031] ii. These systems provide the beneficial external usercharacteristics normally derived from multiple distributed systems (e.g.a local automated attendant is provided, specific language support etc).

[0032] iii. In addition these systems may be engineered to providereliable voice/unified messaging support without strict requirements ondata network availability and quality of service (QoS).

[0033] Such an architecture allows much more flexibility of deploymentfor voice messaging or unified messaging systems.

[0034] There are considerable cost savings to be realized withinenterprises by centralizing the storage of corporate data. Messageswithin e-mail or voice-mail systems derive similar benefits from acentralized storage policy. A geographically distributed Unified orVoice Messaging architecture provides a mechanism to deploy part of theUnified or Voice messaging function co-located with a subscriberstelephone switch while also allowing for a centralized message storagefacility.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The invention is now described by way of example with referenceto the accompanying figures, in which:

[0036]FIG. 1 illustrates an example of a voice or unified messagingsystem at which telephone switches and messaging systems are deployed atmultiple locations, as known in the art;

[0037]FIG. 2 illustrates an example of a voice or unified messagingsystem at which telephone switches are deployed at multiple locationsand associated with a central messaging system, as known in the art:

[0038]FIG. 3 illustrates an example of a voice or unified messagingsystem at which telephone switches and messaging systems are deployed atmultiple locations together with an enhanced central messaging system inaccordance with an embodiment of the present invention;

[0039]FIG. 4 illustrates an example implementation of the enhancedcentral messaging system of the embodiment of FIG. 3: and

[0040]FIG. 5 illustrates an example implementation of a messaging systemdeployed at a location in accordance with the embodiment of FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The present invention is described herein by way of reference toa particular example, and in particular to the example of aunified/voice messaging system. However the invention is not limited inits applicability to the specifics of the examples and embodimentsdescribed herein.

[0042] Referring to FIG. 3 there is shown a unified/voice messagingsystem deployed in a geographically distributed manner and implementedin accordance with a preferred embodiment of the present invention.

[0043] At a first distributed or remote location there is provided a PBX302, connected to an associated voice or unified messaging front-end306. At a second distributed or remote location there is provided a PBX304, connected to an associated voice or unified messaging front-end308. Each of the voice or unified messaging front-ends 306 or 308 may beconsidered to be remote or distributed voice or unified messagingsystems. Each of the remote voice or unified messaging systems 306 or308 is connected to a data network 310, through which there is provideda connection to a common, centralized voice or unified messaging systemback-end 312. The voice or unified messaging system back-end 312 may beconsidered to be a centralized voice or unified messaging system, or acentralized data facility. The centralized voice or unified messagingsystem 312 is, in the described embodiment, further provided with a‘clustered’ front end, which provides, as will be described furtherhereinbelow, front-end functionality equivalent to the functionalityprovided by the front-end voice or unified messaging system 306 and 308.The ‘clustered’ front end is connected to a PBX 314.

[0044] The voice or unified messaging front-end 306 effectively definesa first voice mail domain VMD#1. All users associated with the PBX 302belong to VMD#1. As is discussed further hereinbelow, certain of thevoice or unified messaging functionality for VMD#1 is also providedcentrally by the voice or unified messaging back-end 312. As such, thevoice or unified messaging back-end 312 forms part of VMD#1.

[0045] The voice or unified messaging front-end 308 effectively definesa second voice mail domain VMD#2. All users associated with the PBX 304belong to VMD#2. As is discussed further hereinbelow, certain of thevoice or unified messaging functionality for VMD#2 is also providedcentrally by the voice or unified messaging back-end 312. As such, thevoice or unified messaging back-end 312 forms part of VMD#2.

[0046] In the preferred embodiment of the present invention there isfurther defined a third voice mail domain VMD#3. All users associatedwith PBX 314 belong to VMD#3. All of the voice or unified messagingfunctionality for VMD#3 is provided centrally by the voice or unifiedmessaging back-end 312 and clustered front-end 316.

[0047] Thus, in the embodiment of FIG. 3, users associated with remotePBX 302 are part of VMD#1, users associated with remote PBX 304 are partof VMD#2, and users associated with PBX 314 are part of VMD#3. Furtherremote locations may exist defining further voice mail domains, andindividual voice mail domains may comprise multiple voice or unifiedmessaging systems.

[0048] The functionality of the architecture of the system of FIG. 3 inaccordance with the preferred embodiment of the invention is now furtherdescribed.

[0049] The front-end voice/unified messaging functionality of the voiceor unified messaging front-ends 306 and 308 provide certainvoice/unified messaging functions local to the respective PBX 302 and304 for the respective voice mail domains independent of access to thecentralized voice/unified messaging system back-end 312. The clusteredfront-end 316 provides certain voice/unified messaging functions forusers of VMD#3. The back-end 312 provides certain voice/unifiedmessaging functionality for all voice mail domains.

[0050] It should be noted that although the embodiment specificallydiscloses the provision of PBXs at remote locations, more generally theremote locations can be considered to be provided with a switchingcapability, or telecommunications switch. The invention is not limitedto PBX implementations.

[0051] The front-end or remote system functionality may include, forexample, call answering and automated attendant functionality. Thesefront-end or remote systems may also provide subscriber accesscapability. However the implementation of subscriber access may dependon the data networking characteristics, i.e. quality of service (QoS) ofthe connection from the front-end to the back-end.

[0052] The implementation of the centralised data facility orvoice/unified messaging system back-end system or central system of FIG.3 in accordance with an example embodiment of the invention is shown inFIG. 4.

[0053] Referring to FIG. 4, in a preferred embodiment the voice orunified messaging system back-end 312 comprises a message store 402, adirectory 404, and a plurality of servers 406.

[0054] In FIG. 4 there is shown four front-end servers 406 a to 406 d.The number of servers 406 is implementation dependent, and depends uponthe overall capacity of the system needed to be supported. Additionalservers may be provided to allow for redundancy to improve systemreliability. The servers provide access to the voice or unifiedmessaging system functionality for VMD#3, accessing the system via PBX314.

[0055] For providing centralized voice or unified messagingfunctionality, the centralized voice or unified messaging system isconfigured for all voice mail domains. As shown in FIG. 4 thecentralized voice or unified messaging system is provided with a messagestore 402 and a directory 404. The message store 402 stores messages,such as voice mails and e-mails, associated with system users for allvoice mail domains. The directory 404 stores descriptive attributesassociated with those system users, and system configuration data. Asshown in FIG. 4, the directory 404 stores VMD objects defining systemconfiguration data for each voice mail domain. The directory 404additionally stores subscriber objects, defining the voice mail domainfor each of the system subscribers.

[0056] As shown in FIG. 4, there is provided a central group of servers406 in the centralized system. The servers provide access to the voiceor unified messaging system functionality.

[0057] The implementation of the distributed voice/unified messagingsystem front-end or remote system of FIG. 3 in accordance with anexample embodiment of the invention is shown in FIG. 5.

[0058] Each PBX, such as PBX 302, is associated with a remote voiceserver 504, which may also be considered to be a remote front-end voiceserver. As can be seen, the remote voice server 504 is connected to thedata network 310. The remote voice server 504 is associated with a cachemessage store 506 and a cache directory store 508, illustrated in FIG.5. In accordance with a preferred embodiment of the present invention,and as discussed further hereinbelow, information associated with theusers connected to the PBX 302, and stored in the corresponding messagestore 402 and directory store 404 of FIG. 4, are copied to the caches506 and 508 of FIG. 5, such that a local copy of such information isavailable. As will be further discussed hereinbelow, remote voice orunified messaging functionality is provided by the front-end voiceserver 504 and caches 506 and 508, generally designated by referencenumeral 502 and considered to be the voice or unified messagingfront-end. It should be further noted that each PBX may be associatedwith more than one front-end voice server 504.

[0059] The invention provides, in a first embodiment, mechanisms toallow call answering and automated attendant functionality to operatewhen supported by low-guarantee network connectivity from the messagingsystem back-end. This is achieved by providing the necessaryfunctionality at the front end. As such the provision of thefunctionality is not dependent upon any permanently available back-endor central connectivity. This is achieved by providing the necessarydata, logic and control parameters to achieve such functionality in thecaches. The back-end or central systems provide the primary messagestorage and directory storage and configuration data. All data,messages, user properties and system configuration information isprimarily stored at the back-end or central system.

[0060] The invention provides in a second embodiment a mechanism forreliable subscriber access through direct connectivity to a large‘clustered’ back-end system, in the centralized data storage facility,as provided for in FIG. 4.

[0061] In the following description, the invention is considered in twoparts, although it should be understood that much of the functionalityis shared. The invention is also described by way of reference toexamples of specific feature implementations, but is not limited tosuch.

[0062] In a first embodiment, there is described in accordance with apreferred implementation of the invention the implementation of a callanswering function and an automated attendant function supportedremotely from the distributed centralized data facility, via a low QOSdata network, as illustrated in FIGS. 4 and 5. This relates, moregenerally, to a description of those functions which can be providedindependent of access to the back-end.

[0063] Call answering is a relatively simple process with only limitedrequirement for access to user and system data. The call answeringprocess requires access to data of the following classes:

[0064] I. System properties, including system configuration data such aslanguage availability; and

[0065] II. User properties, such as user configuration data such as‘find-me’ rules and user status (e.g. extended absence), as well asassociated audio greetings.

[0066] The front-end systems associated with each PBX need to maintain acached copy of this data to allow a high degree of quality andreliability in the call answering process regardless of the connectivityto the back-end.

[0067] Preferably a cache management process operates in the background(at a pre-defined time interval, e.g. 5 minutes) and creates a local(and persisted) cache of both system and user properties from theback-end primary stores. As shown in FIG. 4, the directory includesvoice mail domain (VMD) objects and subscriber objects. For VMD objectsthe system configuration parameters for each voice mail domain aredefined. For subscriber objects the VMD identity for each subscriber isdefined. This information is cached at the remote system. The cachemanagement is preferably provided by the front-end or remote system. Atime-stamp is preferably stored for user greetings in the message store.Before an audio greeting is played, the front-end system may check thetime of last-update on the back-end primary version of the greeting. Ifthe front-end cached version of a greeting is correct, then it is used.Otherwise a copy may be fetched from the back-end. In general, callanswering results in recording an audio message. This can be submittedfor delivery in the background with little real-time network capability.

[0068] Automated attendant, when supported by a cache of user and systemproperties as shown in FIG. 5, can also work in the local front-endsystem.

[0069] It is also possible to ‘dynamically cache’ information to reducethe effects of network latency and ‘smooth-off’ bursts of high networkbandwidth requirements. As an example, the n+1th message can bepre-fetched when the nth message is played. This serves, to a point, toprovide improved operation on poor networks but cannot cover allreal-world network (e.g. total WAN failure) conditions.

[0070] Subscribers of VMD#3 access voice or unified messagingfunctionality in a conventional manner, all functionality being providedby the primary data stored in the centralized voice or unified messagingsystem back-end 312.

[0071] As discussed above, voice messaging or unified messagingfunctionality in VMD#1 and VMD#2 is preferably provided by the localizedcached information. Where functionality requires direct centralizedaccess, this can be provided by access to the centralized data facilityvia the data network. Such access may be required for certain subscriberaccess functions.

[0072] In a second embodiment, there is described in accordance with apreferred embodiment of the invention the implementation of a subscriberaccess function for all voice mail domains supported at a sharedcentralized front-end system, as illustrated in FIG. 4, whilstexhibiting the same user characteristics as if calling a local system inthe arrangement of FIG. 1. The advantage of such an arrangement is thatsubscriber access functions may be provided if the link for the remotesystems to the centralized data facility is not available.

[0073] In the preferred embodiment, all subscribers of all voice maildomains may call into PBX 314, which may have a toll-free numberassociated therewith, for subscriber access functions. The system ofFIG. 3 may be an enterprise system of a single organization, and thetoll-free number may be an enterprise wide number for all voice maildomains within the enterprise.

[0074] Existing voice mail systems contain considerable systemconfiguration data which defines the operation of the system. Thisinformation, in the Avaya Unified Messenger and MMA systems, is storedwithin a directory object called a voice mail domain object, in thedirectory of FIG. 4. In the preferred embodiments of the presentinvention, as discussed above, the front-end systems maintain a cache ofthis information, while the back-end systems manage the primary copy ofthe configuration data. In existing systems, and as mentionedhereinabove, multiple front-end systems can be part of a single voicemail domain.

[0075] However, critically, in order to provide centralized subscriberaccess, the front-end systems 316 co-located with the centralized datastores 312 need to be able to be part of multiple voice mail domains. Acall coming into the clustered front-end 316 may be associated with anyVMD, and there is therefore a need to handle the call appropriately forany VMD. The single (large) centralized system of FIG. 4 must be able tooperate as part of all voice mail domains for which subscriber mailboxesare hosted. All voice mail domains are defined by directory objectsstored in the directory systems within the back-end systems and as aconsequence this configuration data is available to both local andcentralized front-end systems. This access to the configuration data ofall voice mail domains is provided by the network interface of FIG. 4,and stored locally in the caches of FIG. 5.

[0076] Subscribers calling into the large centralized front-end system(via the toll-free PBX access) must be identified. This identificationcan be based, for example, on various options:

[0077] a) Identification of the called number. This works if thesubscribers of each voice mail domain are given a different number tocall (possibly an 800 ‘toll-free’ number). In such case theirlocally-valid mailbox number is enough to identify the subscribers astheir voice mail domain can be known. The centralized voice servers maytherefore include a look-up table matching dialed numbers to voice maildomains.

[0078] b) By logging into the system using an enterprise/organizationwide numeric address, and not their usual mailbox/extension number(which is only valid in conjunction with their voice mail domain). Thisaddress allows the user to be identified, from which a VMD can beidentified.

[0079] c) By identifying and recognizing the caller's number, forexample the subscribers cell phone, home phone or work phone numbers maybe stored in a look-up table.

[0080] The clustered or centralized voice servers 406 of FIG. 4 can beadapted to provide identification of the calling party as describedabove to interpret the call for the appropriate voice mail domain.

[0081] Once the voice mail domain (VMD) and the subscriber areidentified the centralised front-end system of FIG. 4 needs to providean interaction which is identical to that experienced by a subscribercalling into a local front-end system of FIG. 1. The front-end system306 thus effectively shifts it's modus operandii based on the voice maildomain information, i.e. the system operates as if it were the voicemail domain identified. All system parameter information is availableand used to provide the required interface.

[0082] Once logged on, subscribers are presented with the correctaddressing options. Addressing a message to a user by theirmailbox/extension number must work correctly. A user within location 1(e.g. voice mail domain VMD#1) addressing a message to “4003”, needs tohave this resolved to the 4003 mailbox (at location 1). A user fromlocation 2 (e.g. voice mail domain VMD#2) may address to the same numberand must have this resolved to a different mailbox. The provision of theclustered front-end 316 of FIG. 3 and 406 of FIG. 4 provides for suchfeatures to work correctly.

[0083] Certain voice/unified messaging scenarios result in the systemlaunching outbound calls. To allow centralized systems to perform thiscorrectly, telephone numbers must be stored in their canonical form.Both types of front-end systems (distributed and centralized) arepreferably configured with rules to ensure calls are correctly dialed.

[0084] In summary, therefore, in embodiments the present inventionprovides for the provisions of distributed messaging systemfunctionality and centralized messaging system functionality, in whichthe distributed functionality is provided by cached stores from thecentralized system, and in which users of the distributed systems mayaccess certain functionality through direct access to the centralizedsystem.

[0085] The present invention is described herein with reference toparticular examples. The invention is not limited in its applicabilityto the examples given. One skilled in the art will appreciate thegeneral applicability of the present invention.

1. A messaging system comprising at least one distributed front-endmessaging system and a centralized data store associated with said atleast one distributed front-end messaging system, in which system thecentralized data store includes means for storing data associated withusers of the at least one distributed front-end messaging system, the atleast one distributed front-end messaging system further including arespective at least one cache means for storing at least a portion ofthe centralized data associated with users of said at least onedistributed front-end messaging system such that at least one messagingfunction can be provided to users of said at least one distributedfront-end messaging system in dependence on the data stored in saidcache means.
 2. A messaging system according to claim 1 wherein there isprovided a plurality of distributed front-end messaging systems eachassociated with a respective plurality of users and each including acache means, wherein the centralized data store is adapted to store dataassociated with all users of said front-end messaging systems.
 3. Amessaging system according to claim 1 wherein there is further provideda centralized front-end messaging system associated with saidcentralized data store.
 4. A messaging system according to claim 3wherein the centralized front-end messaging system is associated with aplurality of users, data associated with said users being stored in thecentralized data store.
 5. A messaging system according to claim 3wherein the centralized frontend messaging system provides at least onemessaging function for users of said at least one distributed front-endmessaging system.
 6. A messaging system according to claim 5 wherein thecentralized front-end messaging system is adapted to identify thefront-end messaging system of a user.
 7. A messaging system according toclaim 6 wherein the centralized messaging system is adapted to identifythe front-end messaging system of a user in dependence on a callednumber, a calling number, or a unique user identifier.
 8. A messagingsystem according to claim 5 wherein the centralized messaging systemprovides access to all stored data associated with said at least onedistributed front-end messaging system associated with the user.
 9. Amessaging system according to claim 1 wherein the centralized data storestores configuration data and message data associated with all users.10. A messaging system according to claim 1 wherein the at least onemessaging function includes call answering.
 11. A messaging systemaccording to claim 5 wherein said at least one messaging function is asubscriber access function.
 12. A messaging system according to claim 1wherein each front-end messaging system is associated with a respectivevoice mail domain.
 13. A messaging system of claim 1 wherein eachfront-end messaging system is associated with a telecommunicationsswitch.
 14. A method of configuring a messaging system comprising:storing, at a centralized location, data associated with all users ofthe messaging system; storing, at at least one distributed location, atleast part of said data associated with users at the at least onedistributed location, and providing at least one messaging function tousers at the at least one distributed front-end messaging system independence on the data stored at the distributed location.
 15. A methodaccording to claim 14 wherein the step of storing the data at said atleast one distributed location comprises the step of caching the data atthe centralized location.
 16. A method according to claim 14 comprisingthe step of providing at least one messaging function to users at the atleast one distributed front-end messaging system in dependence on datastored at the centralized locations.
 17. A method according to claim 16wherein further comprising the step of accessing the centralizedlocation directly.